PULSE
A “pulse” is defined as an electrical signal that changes states from a low voltage (typically less than 0.8V) to a higher voltage (typically 5V). A pulse does not necessarily re-occur. Pulse signals are typically used to either trigger an event or to announce that a specific event has occurred. Note that in the examples below, the pulse may occur at a random time or may never occur, depending on the application.
Example 1: A pulse could be sent to a pump to trigger the pump to begin pumping fluid.
Example 2: A pulse could be sent from a flow meter to announce that a certain accumulated total flow volume has been measured.
FREQUENCY
“Frequency” is defined as a reoccurring electrical signal “wave” that changes states from a low voltage state to a higher voltage state. The frequency of the waves is represented by the symbol Hz (Hertz) and is defined as the number of waves per second of time. An ANALOG frequency signal is represented by a “sine” type waveform. A DIGITAL frequency signal is represented by a “square” type waveform.
The number of pulses per second (Hz) of a frequency signal can be very high. Frequency signals are used to adjust the flow rate of pumps and to define the flow rate of a flowmeter.
Example 1: A frequency could be sent to a pump to define the pump’s motor speed and thereby the amount of fluid being pumped. Because the frequency consists of many pulses per second (typically up to 1000 Hz), the pump’s output speed can react quickly to changes in the frequency.
Example 2: A frequency can be output from a flowmeter to define the instantaneous rate of flow being measured. Because the frequency consists of many pulses per second (typically up to 1000 Hz), the flowmeter’s flow rate display can react quickly to changes in the fluid flow rate.
